Michael J. O'Connell

Reversible water-solubilization of single-walled carbon nanotubes by polymer wrapping

Abstract Single-walled carbon nanotubes (SWNTs) have been solubilized in water by non-covalently associating them with linear polymers, most successfully with polyvinyl pyrrolidone (PVP) and polystyrene sulfonate (PSS). This association is characterized by tight, uniform association of the polymers with the sides of the nanotubes. A general thermodynamic drive for this wrapping is discussed, wherein the polymer disrupts both the hydrophobic interface with water and the smooth tube–tube interactions in aggregates. The nanotubes can be unwrapped by changing the solvent system. This solubilization process opens the door to solution chemistry on pristine nanotubes, as well as their introduction into biologically relevant systems.

In-plane-aligned membranes of carbon nanotubes

We have produced the first macroscopic objects comprised of highly aligned single-wall carbon nanotubes (SWNTs). These objects are thin membranes prepared by producing a suspension of SWNT segments, introducing the suspension to a strong magnetic field to align the segments, and filtering the suspension in the magnetic field to produce an aligned membrane of SWNT. These membranes exhibited natural cleavage planes parallel to the magnetic field. This preparation of macroscopic samples of aligned single-wall nanotubes permits exploitation of their highly anisotropic properties, and will enable measurement of the electronic, thermal, magnetic, mechanical, and optical properties of bulk nanotube materials.